In the field of helmets for warplane or helicopter pilots, it is desirable to produce shells which have the lowest possible mass in order to minimize the forces on the pilot's cervical vertebrae during accelerations of the aircraft. However, the helmet needs to provide sufficient protection, as described for example in military standards such as the standard entitled “Military Aircrew Helmet Impact Standard” published by “UK Ministry of Defence”.
The technological solutions employed for producing helmet shells must remain simple in industrial terms. The conventional solutions for solving this problem are:                the use of thermoplastic materials on their own, injected according to the desired shape;        superimposing a composite shell and a foam absorbing the energy of impacts;        the use of conventional composite materials. The latter are composed of at least two different materials: a matrix which is a resin and a fabric woven according to an “armure” expediently selected according to the intended application. FIG. 1 represents an example of a composite material comprising three layers of fabrics T before coating with the resin R. The manufacturing method is represented in FIG. 2. It comprises three main steps, namely preparation of the resin base, impregnation of the armure with the base, and polymerization of the impregnated structure. It is known that this type of material has much better mechanical properties than the base elements taken independently. The matrix may be a thermoplastic or thermoset. The most conventional case of a composite is the carbon-epoxy composite;        
The solutions offer satisfactory resistances to impacts and penetration with thicknesses of a few millimeters. If there is a desire to lighten these materials, however, the conventional technical means have already been explored. Mention may be made of reducing the proportion of resin, expedient choice of the armure of the fibres and the orientation of the successive plies of the fabric, optimizing the final baking of the monolith or using foams with variable thicknesses.